1. Field of the Invention
This invention relates to a magnetic head employing magneto-resistive effect elements capable of high sensitivity and which permits high density mounting of multi heads.
In the reproduction of signals magnetically recorded in the form of residual magnetization in a magnetic recording medium, the voltage reproduced by the usual magnetic head is very low when the width of the record trace on the recording medium (track width) is very small. Also, where the track width of the magnetic head is greatly reduced, for instance to about several microns, the usual magnetic head encounters many difficulties. Further, it has been difficult with the prior art techniques of manufacture of magnetic heads to arrange such unit magnetic heads into a multi-track arrangement with high precision.
In order to provide solutions to these problems the invention contemplates a high sensitivity magnetic head using magneto-resistive effect elements consisting of ferromagnetic thin plates and construction of a high precision multi-track head by using thin film and photo-etching techniques.
2. Description of the Prior Art
FIG. 1 shows the principal construction of the prior art magnetic heads utilizing the magneto-resistive effect, that is, the fact that the electric resistance of a ferromagnetic material is changed when a magnetic field is applied thereto. In the arrangement of FIG. 1A, a magneto-resistive element 2 consisting of a ferromagnetic thin plate is held in contact with or near a recording medium 1 at right angles thereto (i.e., in the y direction), and electrodes 3 and 4 are provided at the opposite ends of the magneto-resistive element 2 in the longitudinal direction thereof (i.e., in the z direction). In this system, a constant current i is caused to pass between the electrodes 3 and 4 and with a signal field from the recording medium 1 in the y direction a corresponding change of resistance in the z direction is detected from a change of voltage between the electrodes 3 and 4. With this system the intensity of the signal field from the recording medium 1 reduces exponentially with respect to the width of the magneto-resistive effect element 2 in the y direction thereof, and particularly the attenuation of the signal field in the direction of width of the magneto-resistive effect element 2 is extremely large in the region of short wavelengths of the record on the recording medium.
A measure for avoiding such attenuation is to hold the magneto-resistive effect element 2 parallel to the recording medium as shown in FIG. 1B. Although this arrangement substantially eliminates loss in the y direction, friction between the magneto-resistive effect element 2 which is usually a thin plate and the recording medium 1 poses difficulties in the practical use of this system.
In addition, in the above types of head it is structurally difficult to greatly reduce the dimension corresponding to the head track width, and the extreme reduction of the width of element 2 (in the y direction) presents various problems in manufacture and also from the standpoint of the resistance against wear.